An inert electrode is needed to conduct the electrons but it is not part of the redox reaction. You only need an inert electrode (like Pt or C(gr)) if your reactants cant function as an electrode (like I2 and Ce ions). If you have a metal like Zn, Cu or Ag involved you can just use the metal.

Why are inert electrodes used?

The left is the anode and the right is the cathode. 4. It is important to use an inert electrode in this situation because it will not react or participate in the reaction in the cell, just provide a surface area for the reaction to occur.

When should an inert electrode be used?

An inert electrode is required whenever their is no conducting metal. When the participants in a half-reaction are all in the aqueous phase, an electrode, i.e. a solid surface, is needed for the electron transfer.